St Marys Lake near Callaway Water Level
Live lake level, flow, historical records and forecast for St Marys Lake near Callaway in MD, United States, built from official government gauge data.
- Location MD, United States
- Watershed lower potomac
- Primary gauge 01661499 (USGS)
About St Marys Lake near Callaway
St Marys Lake sits in the Lower Potomac watershed in Maryland.
Season by season
The lake’s seasonal pattern is small but clear. The highest month is February, when the typical level is 61.04 ft (18.6 m). The lowest month is September, when the typical level is 60.77 ft (18.52 m). That typical annual swing is 3.2 in (8.1 cm), so the surface usually stays within a narrow band through the year.
For people using docks, lifts, or shallow launches, that means the lake does not move far from its usual range in a normal year. A short set of inches can still matter at the edge of a ramp or the end of a dock.
Records and rises
The record high is 61.88 ft (18.86 m), set in April 2025. The record low is 60.64 ft (18.48 m), set in September 2025. Those two marks sit close together, which matches the lake’s small seasonal swing.
The fastest 24-hour rise is not available in the record here. That leaves one of the most useful warning numbers missing: how quickly the lake can change when conditions turn wet. On a lake with limited range, even a modest rise can be the difference between a dry edge and water at the bank.
Reading the hero number
This page’s hero number compares today’s reading with the median for this calendar day, rather than showing raw elevation by itself. That matters because a lake can look “high” or “low” in absolute terms and still be normal for the date. The day-median puts today’s level against the station’s own history.
The station is operated by the U.S. Geological Survey. With about 2 years on record, the comparison is useful, but it is still a short record.
How this page is built
Readings come from official government gauges and are rolled into daily records: the daily mean, high and low for every day on record. Each calendar day gets its own baseline from the full history, so the level you see is compared against what this specific date usually looks like rather than an annual average.
How Nibi Metrics works · Water stories
Nibi Metrics - live water levels, flow, and forecasts for lakes and rivers across Canada, the US and the UK
Real-time water levels, forecasts, and alerts for lakes and rivers across Canada, the US and the UK. Built on official government data.
Nibi Metrics tracks more than 13,000 gauged lakes and rivers across Canada, the United States and the United Kingdom, reading directly from official federal monitoring networks: the Water Survey of Canada, the United States Geological Survey, Quebec's provincial hydrometric network, and the Environment Agency for England. Every number on the platform is measured, not modelled - taken from a government gauge on the water itself and compared against that location's own historical record for this exact date.
What you can see for any monitored lake or river
The level right now, in feet or metres, updated as the source agency publishes new readings - for many stations that is every five to fifteen minutes. How today compares to typical: every location carries its own typical-for-this-date band built from its historical record, so a reading is never just a number - it is above, below, or near what this water usually does on this calendar day. Which way it is moving: a measured RISING, FALLING, or STEADY verdict computed from the gauge's own recent readings, with the rate of change - the difference between a flood ending and one beginning. What comes next: level forecasts up to 72 hours ahead, driven by the gauge's recent behaviour, upstream water, and quantitative precipitation forecasts, alongside live radar, lightning, and weather for the surrounding region.
Alerts that watch the water for you
Set a threshold on any location - a level, a distance above typical, or a rate of climb - and Nibi emails or notifies you the moment the gauge crosses it. Cottagers use it for spring freshet, anglers for river conditions, marinas and municipalities for operations. The scanning runs around the clock against the same measured data shown on every page.
Where Nibi comes from
Nibi means water in Anishinaabemowin. The platform began at a family cottage on Lake Muskoka, Ontario, where the spring melt floods the shoreline most years and the only forecast was standing on the dock, looking, and guessing. It grew into an independent, member-funded platform run by Muskoka Research Inc. - no investors, no data resale, and a privacy policy shorter than most cookie banners. The core data is free for everyone, forever; paid plans add automation like multi-location alerts, deep history, and reports.
Coverage
Nibi spans the continent: every Canadian province and territory with active federal gauges - from Vancouver Island rivers to the Muskoka lakes, prairie reservoirs, and Quebec's hydrometric network - and the United States from Maine to the Texas Hill Country, the Ohio Valley, and the Pacific Northwest. Coverage grows where the water news is: when a basin floods, its gauges join the platform with their full historical records attached. Many stations report every five to fifteen minutes; most report at least hourly; every page states exactly when its gauge last spoke.
Free forever, funded by members
The core promise is simple: the water data is free, for everyone, forever. Live levels, maps, radar, and recent history never sit behind a paywall. Paid plans fund the platform by adding automation - multi-location alerts, decades of history, longer forecasts, and PDF reports - so the people who need more carry the cost for everyone who just needs to check the lake before driving up. There are no investors and no advertising deals shaping what the data says.
Water Stories
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Inside the freshet cycle that puts Manitoba shorelines at risk each year - and why 2026 broke the script.
The science of snow water equivalent and why it drives the season ahead.
What the numbers on the measuring stick actually tell you.
Why Central and South Texas rivers go from gravel beds to fifty-year records in an afternoon - including July 2026 on the Nueces.
One percent, every year, forever - unwrapping hydrology's most misunderstood phrase, and how it differs from our own percentiles.
How every number is computed - About the platform
